Mattermost

Mattermost is a secure, open source collaboration platform that provides messaging, file sharing, and workflow orchestration for teams. It's widely used as a self-hosted alternative to Slack and Discord, especially by organizations that need their communication data to stay in their own environment.

Both offer channels, direct messages, and group communication. Mattermost is focused on workplace collaboration — with deep integration into development workflows like GitLab, Jira, and GitHub — and is designed to be self-hosted for security and compliance. Discord is more consumer- and community-oriented with built-in voice channels and gaming features.

Yes. Mattermost is explicitly designed for self-hosting. You can deploy it on your own servers using binary packages, Docker, or Kubernetes, keeping all data on infrastructure you control. There are also cloud and paid enterprise options if you prefer managed hosting.

Yes. Mattermost supports voice calls, video calls, and screen sharing through its built-in Calls feature. It also integrates with common tools like Zoom and Microsoft Teams if your organization prefers to use a dedicated conferencing solution.

Mattermost provides features for secure collaboration including role-based access control, multi-factor authentication, LDAP/SAML/AD single sign-on, eDiscovery and audit logs, and end-to-end encryption. It's used by government, defense, and enterprise organizations that require strict data residency and compliance.